Copyright 1999
Chapter 4
WINERY MATERIALS
Various materials are added to wine throughout the winemaking process. These materials are used to solve specific wine problems. For example, bentonite is always added to white and blush wines. The bentonite removes excess protein and prevents protein from forming a haze after the wine is bottled. Small amounts of sulfur dioxide are added when the grapes are crushed, and small additions of sulfur dioxide continue until the wine is bottled. Sulfur dioxide helps control the growth of microorganisms, and it reduces the effects of oxidation. Wines fermented from apples and stone fruits often contain excessive amounts of pectin. The pectin makes the wine difficult to clarify, so winemakers add enzymes to break down the pectin. The most common wine additives are sulfur dioxide, fining agents, stabilizing materials and wine preservatives.
COMMON WINEMAKING MATERIALS
Winemakers must use care when selecting wine additives. Wine is a food, and any substance added during the winemaking process must be a "food grade" material. Most materials used in winemaking are also used throughout the food and beverage industries. These materials are widely used and available to the winemaker as normal commercial products. A few wine additives are unique to the winemaking industry, and sources of a few materials may be difficult for home winemakers to find.
Many winemaking materials are supplied by the manufacturer in dry granular forms. These materials are usually shipped in heavy paper or plastic bags containing about 50 pounds of material. With a few exceptions, winemaking materials have a long shelf life. Many winemaking materials can be kept for several years when placed in tightly sealed containers and stored at reasonable temperatures.
Home winemakers can reduce their winemaking costs by getting together and purchasing frequently-used winemaking materials in commercial quantities. Materials purchased in small quantities often cost three or four times the bulk price, so the savings can be significant. Reagents for wine testing and yeast and sulfites are exceptions, and fresh supplies of these materials should be purchased each season. The characteristics of several common winemaking materials are briefly discussed below.
Anti-foam
Anti-foam is a clear, oily liquid. This is a silicone product, and it has no smell or taste. Anti-foam is used to prevent foam from overflowing containers during active fermentation. About 250 milliliters of anti-foam added to a 1000-gallon wine tank will reduce foaming to a minimum. This material is completely inert and does not react with the wine in any way. Most of the anti-foam added will disappear when the wine is racked. Even if a few drops remain, they will be removed when the wine is filtered.
Ascorbic Acid
Ascorbic acid is vitamin "C." Winemakers add ascorbic acid when wines contain di sulfides. In larger amounts, di sulfides can smell like a skunk. Smaller quantities give wine a rubber or garlic smell. When very small quantities are present, di sulfides can give wine a vague, "dirty" odor. At even lower levels, di sulfides often do not produce a specific odor. Sometimes they are not detectable, but minute quantities of di sulfides can kill the normal bouquet of a fine wine.
When ascorbic acid is added to wine, it reacts with the di sulfides, and the di sulfides are converted into a material called mercaptan. When all of the di sulfides are converted into mercaptan, the winemaker adds a very small quantity (0.05 to 0.5 milligrams per liter) of copper sulfate. The copper sulfate removes the mercaptan from the wine. This treatment is only effective when the ascorbic acid is added to the wine several days before the copper sulfate addition.
Many Australian winemakers use ascorbic acid as an anti oxidant when bottling wine. The ascorbic acid is used in combination with sulfur dioxide.
Calcium Carbonate
Sometimes, grapes grown in cold climates contain too much acid. Then winemakers often use calcium carbonates to reduce the acid content of juice before fermentation. This material is occasionally used to reduce the acid content of finished wines by small amounts. However, when carbonates are used to reduce the acidity of a finished wine, they can change wine flavors, raise pH and cause other problems. Grapes grown in warm climates are usually low in acid, so carbonates are seldom used with warm climate fruit.
Citric Acid
Citric acid is one of the work horse materials in the winery, and it is used for several different purposes. Citric acid is mixed with sulfite powder and water to prepare sulfur dioxide solutions. Sulfur dioxide solutions are used to sterilize winery pumps, hoses, filters and other winery equipment. Sulfur dioxide solutions are also used for wet barrel storage. Winemakers use weak (1 percent) citric acid solutions to remove the "paper" taste from new filter pads. Stronger solutions (5 percent) of citric acid are often used to sanitize bottling equipment.
Sometimes, citric acid is added to finished wines specifically to increase acidity and improve acid balance. In small quantities, it provides a fresh, citric characteristic, and the citric quality is often appreciated in white table wines. Nevertheless, bench trials should always be done before making any large additions of citric acid. Significant additions of citric acid are seldom made to red wines. The citric taste does not seem appropriate in most red wines. About half a gram of citric acid per gallon is often added to commercial wines to improve long term stability.
Diammonium Phosphate (DAP)
Diammonium phosphate is a major ingredient in many proprietary yeast foods. It is added to juice or must before fermentation to supply extra nitrogen. The additional nitrogen encourages rapid yeast growth and more dependable fermentations. California Chardonnay grapes are often deficient in nitrogen, and many winemakers add DAP to all Chardonnay juices to help the yeast complete fermentation and not leave residual sugar in the wine. Juices lacking nitrogen can cause another problem. Some yeasts produce excessive quantities of hydrogen sulfide when a juice lacks sufficient available nitrogen. Here, winemakers add DAP to provide extra nitrogen to reduce hydrogen sulfide formation.
Fumaric Acid
In the past, winemakers often added small quantities of fumaric acid to their red wines. The acid prevented malolactic fermentation from occurring after the wine was bottled. However, since sterile filtration equipment became widely available, fumaric acid is seldom used commercially. Many home winemakers lack filtration equipment, so home winemakers continue to use fumaric acid to control ML fermentation. The customary dose levels range from one to three grams of acid per gallon of wine. Bench testing should always be done before fumaric acid is added to wine. This acid can improve the taste of some red wine, but sometimes fumaric acid produces unusual or off-flavors.
Malic Acid
Vines release malic acid (by respiration) throughout the ripening season. When grapes are grown in hot regions, little malic acid remains by harvest time, and sometimes winemakers add malic acid to white wines to improve the ratio of malic and tartaric acid. Small additions of malic acid raise the total acidity and often give white table wines a pleasing apple-like freshness.
Pantothenic Acid
Yeasts often produce excessive quantities of hydrogen sulfide when grapes are deficient in pantothenic acid. Consequently, some winemakers add very small quantities of this material to juice or crushed grapes before starting fermentation. Pantothenic acid is a common vitamin, and it can be purchased in any drug store.
Pectinase (Pectic Enzyme)
Sometimes, commercial wineries use enzymes to increase the amount of free run juice when crushing white grapes. The enzymes break down the cells in the grape pulp, and the juice is released. The additional free run juice reduces the number of press loads, so pressing is quicker after an enzyme treatment. Home winemakers, using small basket presses, use pectic enzymes to make white grapes easier to process. Pectic enzymes are also used to prevent pectin hazes from forming in wines made from fruit or from grape concentrate. Excessive quantities of enzymes can produce off-odors and bad tastes. The manufacturer's directions should be followed carefully.
Potassium Bitartrate
Sometimes, small quantities of potassium bitartrate (cream of tarter) are added to young wines during the cold stabilization treatment. The potassium bitartrate crystals speed the precipitation of excess tartrate material from the wine. The time required to stabilize the wine is shortened, and winery refrigeration costs are reduced. One to four pounds of potassium bitartrate per 1000 gallons of wine is the normal dose.
Potassium Carbonate
Potassium carbonate is often used to deacidify juice and wine instead of calcium carbonate. However, when this material is added to wine, the potassium content can be increased significantly. The additional potassium can cause increases in wine pH, so potassium carbonate must be used carefully.
Besides increasing pH, a stability problem sometimes occurs because the potassium reacts with tartaric acid in the wine. Potassium bitartrate is formed, and unless this material is removed, it can precipitate out of the wine after bottling. Because of this instability problem, potassium carbonates should not be used after wine has been cold stabilized.
Potassium Caseinate
Potassium caseinate is a common, wine fining material. This material is used to reduce the tannin content in red wine, and it is used for white wine clarification. Potassium caseinate is also used to remove odors and brown colors from oxidized white and blush wines. Sometimes, this material is effective for removing excessive oak character from white wines. When added to wine, potassium caseinate reacts with wine acids and coagulates quickly. Fining is more successful when a caseinate-water solution is injected into the wine under pressure. Then, a very fine suspension is formed, and better mixing is achieved. Some home winemakers mix the dry powder in water and use a large syringe to "inject" the solution into the wine.
Potassium caseinate can strip desirable wine flavors and give wine a "cheese" taste when excessive quantities are used. Normal dose levels range from 1/10 to 1/4 gram per gallon, and bench trials should always be done.
Potassium Metabisulfite (Sulfite)
Home winemakers use potassium metabisulfite crystals to introduce sulfur dioxide into their wines. Small quantities of sulfur dioxide are used to control wine microbes, and sulfur dioxide also reduces wine oxidation. When sulfite is added to wine, it produces about half its weight in SO2 (about one gram of sulfur dioxide is produced when two grams of sulfite are added to the wine).
Strong sulfite solutions are used to sterilize just about everything in a winery. One teaspoon of sulfite powder and two teaspoons of citric acid in two gallons of water makes an effective solution for sterilizing equipment, and some home winemakers use this solution to sterilize bottles just before they are filled with wine. Inert, oak barrels can be stored full of water safely using a sulfite solution. One cup of citric acid and one cup of sulfite crystals are added, and then the barrel is filled with clean water.
Potassium Sorbate (Sorbate)
Home winemakers use potassium sorbate to stabilize wines containing residual sugar. The sorbate does not stop the yeast from fermenting the sugar, but it can prevent the yeast cells from reproducing. Consequently, sorbate is only effective when most of the active yeast cells have been removed from the wine by racking or filtering. The usual procedure for using potassium sorbate is to clarify, stabilize and age the wine. Then the wine is sweetened, and the sorbate is added at bottling time. Potassium sorbate will not stop active fermentations.
For most people, the taste threshold of sorbate is 200 or 300 milligrams per liter of wine. However, some people are more sensitive to the taste of sorbate, and a small fraction of the population can detect less than 50 milligrams per liter. Fortunately for the winemaker, many people sensitive to sorbate do not find its taste objectionable in wine.
The normal dose level is 200 to 250 milligrams of potassium sorbate for each liter of wine (about one gram of sorbate per gallon of wine). If too little sorbate is added, the wine will probably start to ferment. If too much sorbate is added, the quality of the wine may be adversely affected. Dose levels of more than 250 mg/l can produce noticeable changes in wine taste and odor.
Sodium Bisulfite
Sodium bisulfite is an inexpensive source of sulfur dioxide for small wineries. It provides the same amount of SO2 as potassium metabisulfite, but the sodium compound is less expensive. Sodium bisulfite is mixed with water and used for sterilizing all kinds of winemaking equipment and for wet barrel storage. Since it adds sodium, this material is usually not used as a source of sulfur dioxide in wine.
Both potassium metabisulfite and sodium bisulfite are very sensitive to water, and both compounds should always be stored in tightly sealed containers. Even when stored in sealed containers, these materials can degrade rapidly, and much wine has been spoiled by home winemakers using spent sulfite powder. Old sulfite powder should be discarded, and a new supply purchased each crush season.
Soda Ash
Soda ash (sodium carbonate) is one of the primary cleaning agents in the winery. It is used to clean and sanitize equipment, tanks, pumps, hoses and even barrels. Soda ash in water produces a strong caustic solution, and a soda ash solution is particularly useful for removing heavy tartrate deposits from the surfaces of wine storage containers. All soda ash solutions must be carefully rinsed to remove the residue. Home winemakers often use soda ash to soak labels off old wine bottles.
Tartaric Acid
Winemakers add tartaric acid to juice or must to raise acidity and lower pH. Large acid adjustments should be made before fermentation is started. An addition of four grams of tartaric acid per gallon of juice will raise the TA about 0.1 percent. Calculated acid additions are seldom accurate, and calculated acid values should not be relied upon. A small sample should be tested before making large acid additions.
Care must be taken when tartaric acid is added to wine late in the winemaking process. If much tartaric acid is added, the wine may need to be cold stabilized again. Otherwise, tartrate crystals may form in the bottled wine.
Thiamine
Thiamine is vitamin B-1, and it is essential for healthy yeast growth. Winemakers often add B-1 and other vitamins to juice before starting fermentation. Thiamine is an ingredient in proprietary "yeast foods."
Trisodium Phosphate (TSP)
Trisodium phosphate is a popular cleaning material for all types of winery surfaces. This material is inexpensive, effective, and it washes away easily. A chlorinated form of trisodium phosphate is also available, and the chlorinated form is a potent sterilizing material. In many commercial wineries, chlorinated TSP is the material of choice for decontaminating large, stainless steel, wine storage tanks.
Viniflora Oenos
Viniflora Oenos is a freeze-dried culture of malolactic bacteria. Most ML bacteria are supplied in liquid form, and several days are needed to prepare a "starter." Viniflora Oenos has gained popularity rapidly because it can be added directly to the wine in dry form to start malolactic fermentation.
Yeast Extract
Yeast extract is added to juice to prevent stuck fermentations by stimulating healthy yeast growth. Yeast extract provides additional vitamins, amino acids, etc. It is more effective when added before fermentation is started. Yeast extract is a major ingredient in many proprietary yeast supplements.
SUMMARY
Winemakers add different materials to wine throughout the winemaking process. These additions are made deliberately to improve color, clarity, stability or general wine quality. Each fining material can affect wine characteristics differently. Often one characteristic is improved at the expense of another, so fining wine is usually a compromise of some kind. Considerable winemaking experience is needed before wine fining materials can be used effectively. The types of material and the quantities to be used are usually determined by testing a small batch of wine and observing the results. When the desired results are obtained, appropriate additions are made to the main lot.
Winemaking materials should be kept in tightly sealed containers, and then the containers should be stored in a cool, dry place. With a few exceptions, like yeast and sulfite, most winemaking materials can be kept for several seasons, and purchasing winemaking materials in bulk quantities results in significant savings.
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